Telegraph system



' Julie 16, 1931. Y J, BELLAMY 1,810,198

TELEGRAPH SYSTEM Filed Nov. 30, 1928 2 Sheets-Sheet 2 InLrEnZur' Juhfi I. 5:22 m

Patented June 16, 1931 so STAT rrc 1 JOHN I. BELLAMY, OF BROOKFIELD, ILLINOIS, ASSIGNOR TO RESERVE HOLDING COM- PANY, OF KANSAS CITY, llIISfiO'URI, A CORPORATION OF DELAWARE TELEGRAPH SYSTEM Application filed November 30, 1928. Serial No. 322,631.

The other objects as well as the several feal tures of the invention will become apparent upon a further perusal of the specification in connection with the accompanying drawings forming a part thereof and comprising Figs."

l'to v11. These drawings show by means of the usual circuit diagrams and by means of mechanical drawingsa suflicient amount of apparatus used in a telegraph system employing two-way repeaters to enable the several m stood. V v

Referring now particularly to the drawings, Fig. 1 shows two telegraph lines interconnected by a repeater employing twosingle wound relays, each arranged to repeat impulses from its associated line into the other line' Fig. 2 shows a similar repeater having, in addition to the two relays of-Fig. 1, two repeating relays each arranged to respond to control by its associated line relay to repeat impulses into the other line;

Fig. 3 shows a two-relay repeater similar to the repeater of Fig. lexceptthat an alternative-holding arrangement is employed involving a second winding on each relay rather .than the arrangement of Fig. 1 which holds the outgoing repeating relay through its line winding and an associated resistance; Fig. 4 shows a two-relay repeater arranged so that it has only front contacts (contacts that are closed while the relay is operated), the holding of the outgoing line relay being accomplished by removing a shunt from 59 around the holding winding thereon'rather than by closing a holding circuit for the out going relay as in Figs. 1 to 3;

Fig. 5 shows a repeater similar to the rep'eater of Fig. 4; except that the holding windings have been removed from the line relay cores and placed on separate holding cores;

Figs. 6 and 7 show the mechanical arrangement between coil 503 of Fig. 5 and line relay 5042; i

Figs. 8 and 9 show a modification of the arrangement shown in Figs. 6 and 7;

Fig. 10 shows a modification of the circuit of Fig. 5 in that theholding coils are made into relays, being provided with contacts so, that each of them, upon becoming energized,

shunts the contacts of its associated line relay 1 so as to prevent any-harm being done by the outgoing line relay falling back during repeating of impulses instead of holding the armature of the outgoing line relay operated as is done when thefcircuit of Fi 5 is applied to the mechanical structure of *igs .6 and 7 o'r- Figs. 8 and 9; and

lays are differentially wound and operate responsive to the opening of the circuit through one winding.

Referring now particularly to Fig. 1, the

operation of the apparatus shown therein will now be explained. The line relays 102 and 103 of the repeater, as well as the main line relays 101 and 112 at the station endsof the line, have been shown non-operated.

Likewise the keys K1 and K2 have been shown open. The showing wasmade in this way because it was thought that the operaboth lines open both relays will not be back as shown, but one ofthem will be operated.

It will now be assumed that the battery is disconnected at relays 102 and 103 and that relays 102 and 103 are both normal for this reason and that the keys K1 and K2 are'both up. When the battery is reconnected to relays 102 and 103 under this condition they M modifications of the invention to be underi "Fig. 11 shows a circuit similar to that 'shown in Fig. 10 except that the holding reboth attempt to operate. One of the relays always operates before the other, it being almost a physical Inpossibility to secure two relays which operate in exactly the time. The first relay to operate opens the circuit of the other, prevent 1g the other from operating. It will be assumed that relay 103 succeecs in operating, from which it follows that relay 103 at armature 100 'orces the spring 111 out of 0115 igement with the contact 110, opening the local circuit :tor relay 102 from the associated battery connection to the ground connection through me resistance 105. The engagement of armature spring 109 with spring 111 connects relay 102 to the associated line west. key K1 is open at th' line, this ha no effect. If it be assumed that the operator at the west station closed the key K1 there is a flow of current over the line and relay 102 operates. Upon operating, relay 102 connects relay 103 to the line east at cont-acts springs 106 and 108, at the time opening the local circuit of relay 102 at contact springs 107 and 108. I This results in a deenergization of relay 103 because the line east is open at the key Y2. Relay 103 deen gizes and opens the line west, at the same time closing a local holding circuit for relay 102 through, (ontacts 111 110 and resistance 105. 'Ihemomentary current low over line West is thus inter ted. The only result noticed at the stat on line west is a momentary tapping of the main line relay 101, which probably results in a click on the associated sounder assumed to be connected to the contacts of relay 101. It will thus be seen that an attempt of an operator having control of his line to send while th other line is open results in the control being shifted to the opposite line.

It will now be ssumed that the operator at the key K2 his key K2, with'the k i K1 closed a1 manner just poi 102 on Zed in the relay 103 operates over line east and this occurs,

through contacts 106 and 103 and connects relay 102 to the line west, at the same time opening the local holding circuit or 102. It may be pointed out that this is or course tae normal condition of the line. both keys b ing closed while the line is idle so that eith r operator may send at any time. Relays 101 and 112 are both operated.

It will now be assumed that the operator at the key K2 desires to send a message to the operator at the key K1. V hen the key K2 is opened, relay 112 falls back and relay 103 falls back and opens the line west, whereupon the current flow in line west ceases and relay 101 falls back. Relay 102 is at the same time transferred to a. local locking circuit through contacts 111 and 110 and resistance .105 so that relay 102 rei'nains operated and maintains line east closed at contacts 106 Since the broken.

and 108. Each time the key K2 is closed in sending, relay 112 reoperates, ano relay 103 reoperates and reconnects the relay 102 to the line west, sending an impulse over the line, at the'same time opening the local holding circuit of relay 102. When the sending operation is over the operator at key K2 closes the key.

Similarly, if the operator at the key K1 desires to transmit to the operator at the key K2, he opens the key whereupon relay 102 falls back and opens the line east, permitting 112 at the key K2 to fall back. Belay 102 at contact springs 10'1" and 108 closes a local circuit for relay 103 so that this relay does not fall back. Therefore, the line is maintained closed by relay 103 at contacts 109 and 110. It is required in telegraph practice that a receiving operator shall be able to break his line and the line of the sending operator in case he misunderstands a portion 01 the message, forexample. If it be assumed that the operator at key K2 is sending to the operator at the key K1 and that the operator at the key K1 wishes to break in, the operator at key K1 opens his key. If the key is opened at a time when the key K2 is open, nothing occurs because there is no current flowing in either line at that time. Relay 102 is at this time locked up through resistance 105, and relay 103 is deenergized. When the key K2 is again depressed under this condition, relay 103 reoperates and transfers relay 102 from the local holding resistance to the line west, whereupon relay 102 falls back owing to the key K1 being open. Upon falling back, re-

lay 102 closes a local holding circuit for rekey K and waits for the message from the operator at the key K1, who upon closing his key K1 to start the transmission brings about an energization of relay 102 which reconnects relay 103 to the line east instead of to the resistance 104, whereupon relay 103 operates again and relay 112 at the key K2 picks up. The operator at key K1 now sends to the operator at the key K2, the impulses being repeated at contacts 106 and 108 and relay 103 being connected in a local holding circuit through resistance 104: on each break by contacts 107 and 108.

It will be noted that the springs of relay 102, as well as the springs of relay 103, are so arranged that upon each movement of the armature of the relay, upon energization 0r deenergization, all three springs of the relay come together before the two in contact are This combination is technically known as a make-before-break spring combination. This combination is used here so in a situation where both lines have aboutv the same resistance, leakage, and inductance,

the use of make-before-break contacts is not required, and'relay 102, for example, may be connected to the line through a pair of contacts like 109 and 111, while it may be connected toresistance 105 through a separate pair of separately adjustable contacts such as,-for example, the inner upper pair of 302, Fig. 3. This has the advantage that therelay does not have to travel so far in energizing or deenergizing, owing to the fact'that the making operation and the breaking op eration may be taking place more nearly at the same time. p

Referring now particularly to- Fig. 2, the repeater shown therein is operated on the same principles as the repeater shown in Fig. 1, the relays 202 and 205 corresponding respectively to the relays 102 and 103. The difference is that the repeating contacts have been removed from the line relays and placed onthe repeating relays 203 and 204, while the line relays have only a single pair of contacts each.

repeating relays 203 and 204, which have the The reason for this is that the more complicated spring combination, operate in a local circuit of a substantially unvarying condition, whereas the line relays work under conditions that vary with the weather and numerous other things. The repeating relays can be adjusted once to repeat the same length of impulses receivedand that adjustment need not be changed except at infrequent intervals to take care of mechanical wear, if any. On the other hand, the adjustment of the line relay is more critical and it is advantageous to have'a line relay with only a single pair of contacts so that the-armature of the relay can be adjusted witha short stroke, experiment having demonstrated that a line relay such as 202 will respond with the same adjustments to a wider range of line conditionsthan a line relay like 102 with a make-before-break combination requiring a longer armature stroke.

Referring now more particularly to the operation of the arrangement shown in Fig.

'2, it may be conveniently assumed that the battery is connected for the firsttime to relays 202205 with all'other connections complete and with the keys K3 and K4 open as shown. vIlnder this condition, a circuit is completed for relay 205 through the resist ance 206 and contacts of relay 203, and a similar circuit is completed for relay 202 through resistance 20'? and contacts of repeating relay 204. Relays 202 and 205 both operate to- 'gether and each one'closes the circuit of the associated repeating relay. 7 Each repeating relay, if it succeedsin operating fully before I it ishalted, opens the circuit of the other line relay. In practice, one pair of relays operates ahead of the other pair of relays and stops the repeating relay of the other pair before it completely operates. It will be assumed that relays 204 and 205 succeed in operating before relays 202 and 203 have operated, with the result that relay, 204 connects relay 202 to the line west instead of its former circuit through resistance 207. The line west being open at thekey K3, relay 202 falls back and opens thecircuit of relay "203 before it is completely operated, with the result that the circuit of relay 205through resistance 206 remains established." In case the key K3 is now closed, relay 202 operates over the line west and relay 203 operates as a result and shifts the outgoing line relay 205. from in connect-ion with the resistance 206 to the line, whereupon relay 205 falls back because the key K4 is open. Upon falling back, relay 205 reenergizes relay 204, whereupon relay 202 is shifted from in connection with line west to its former circuit to ground through resistance 207 The relays remain in this condition andthemomentary current flow over the line west as a result of the operation of the key K3 is now termi- Inated.

Assume now that the key K4 is closed with the key, K3 closed and with relays 202 and 203 operated and relays 204 and 205 nonoperated as above pointed out. -,Re1ay 205 operatesover line east and closes a circuit for rel'ay 204. Relay 204 shifts relay 202 from its connection with resistance 207 to the line west, and relay 202 remains operated over the line'west. The current flow over line west energizes relay 201. Current is now be effected and in that the resistances 104 and i 105 and theirseparate mountings are eliminated. In the case of Fig. 1, the resistances 104 and 105 have to be proportioned low enough so that the line relays will hold up through them. This means that substantially full line current of thereabouts must pass through these resistances. If the resistances are wound in a very small space the heat burns the insulation 01f the wire. Therefore,

self-coolingresistances must be supplied,

which often take up considerable mounting space in comparison to that required in an ordinary relay. In the case of Fig. 3, however, the outgoing line relay (the relay 302, for example, when an impulse is being repeated from the line west to the line east by an open key at the line west station) is held in a local circuit through an auxiliary winding, the lower winding. lC-his winding is made of high resistance and draws little current so that there is no appreciable heating and a saving in battery consumption is etfected as well as a saving in a special. resist ance mounting. Since the contact pairs of relays 301 and 302 are separately adjustable, they may be adjusted so that they make before they break or otherwise as the occasion may demand.

It will be understood, of course, that the same holding arrangement may be employed in connection with Fig. 2 in which case relays 202 and 205 would be of the double wound variety and the holding circuit would include contact arrangements the same as those employed in Fig. 3.

Referring now particularly to Fig. 4, the repeater shown therein is an improvement on F 1g. 1, paralleling the improvement shown 1n Fig. 2. The heavy line-relay-contact problem of Fig. 1 is attacked in the way above .described in connection with Fig. 2, and in Fig. 4 is attacked in a radically ditlerentmanner. In Fig. 2 it will be recalled each impulse must be repeated by a repeating relay. The arrangement of Fig. 2 is very good as long as the battery supplying current to the repeatmg relays remains at the same potential. In case the potential of this battery is not closely regulated, however, the length of the impulse repeated by the repeating relay may vary considerably. For this reason, the arrangement of Fig. 4 has been produced employing two line relays and no repeatingrelays, the line relays being provided with make contacts only, no break contacts being used as is the case in Fig. 1. In Fig. 4 each line relay 401 and 402 has its line winding as in the case of Fig. 1, and each line relay has in addition a holding winding as in the case of Fig. 3. In the arrangement of Fig. 4, however, the circuit of the holding winding is normally closed and the holding winding is deenergized by short circuiting it, the current-limiting resistances 403 and 404 being used to prevent a short circuit on the station battery. With relays 401 and 402 both energized over their respective lines, it will be noted that the holding winding of relay 401 is short circuited at the upper contacts of relay 402 and that the holding winding of relay 402 is short circuited at the lower contacts of relay 401. An interruption in either line results in a deenergization of the associated line relay which interrupts the distant line and at the same time removes the short circuit from around the holding winding of the outgoing relay, preventing the outgoing relay from falling back. When this modification is used, care must be exercised in designing the holding windings of relays 401 and 402 so that when the holding winding of a relay is short circuited a noticeable retarding eilect will not be exerted upon the relay by the short circuited winding. With a given number of turns in the holding winding, the higher resistance of the winding, the less the retarding effect. On the other hand, with the same size and material used in the wire from which the winding is made, the fewer the turns in the holding winding the less the retarding effect. In either case, the winding which has the least retarding effect has the east holding eii ect. The holding etlect of a given winding can be increased by increasing he battery potential employed to send current through the holding winding. From the foregoing remarks, it will be understood that a holding winding can be secured, having just sulllcient holding power which will not have an appreciable or detrimental retarding effect upon the repeating action of the relay.

Referring now particularly to Fig. 5, which modification is further improvement on the arrangement in Fig. 4, it may be pointed out that Fig. 5 is the same as the arrangement of Fig. 4 except that the holding windings are removed from the line relays and are placed on separate magnetic cores. More in particular, relays 501 and 504 are the line relays and correspond to relays 401 and 402 with special reference to the upper windings of the latter relays coils 502 and 503 are holding coils and may correspond, respectively, to the lower windings of relays 401 and 402; and the resistances 405 and 406 correspond, respectively, to the resistances 403 and 404. It is obvious that tl e arrangement of Fig. 5 must fall short of itsobjective unless some mechanical or electro-magnetic connection is employed in connection with the holding coils .502 and 503 to maintain the contacts of the rethese drawings show two views of holding coil 503 and the line relay 504 of Fig. 5. The relays shown in Figs. 6 to 9 are of the type used extensively in automatic telephone systems and shown in Figs. 51 and 58 of the illustrations in Automa tic Telephony, a

book by Smithand Campbell, published by the McGraw-Hill Book Company, Newposeof the screw andlock nut being to pre- Vent the iron armature irom striking the.

core, providing an air gap soas to insure a switch release of the armature when the current in the coil ceases. -The screw 602 is long enough so that the iron member 601 may be secured firmly to armature 604 by the lock nut so that when the coil 503 is energized the iron member 601 is attracted to hold the armature 604 operated. The residual screw 603 and associated lock nut may be provided in-the end of the iron member 601 to prevent this member from striking the core of coil 503 if desired. WVith the armature 604 of relay 504 thus electromagnetically extended over the core of relay 503, and with the same cooperation between relay 501and the coil 502, a break in either line results in a restoration of the corresponding'line relay, as the holding coils are normally deenergized, resulting in an' opening of the other line and in the removal of theshunt'it'rom around the holding coil of the outgoing line, holding the armature of the outgoing relay operated.

It may be pointed out that mounting the holding coil 503 below the relay 504 instead of to the right of relay 504 results in a betteroperation of the armature of relay 604 than in the alternative arrangement on account of the greater inertia that member-601 would impart if it were moved through a longerv are as would be the case were the 0011 503 mounted to the right of relay 504. 7

Referring now to'Figs. 8 and 9, it will be pointed out that the structure shown therein has some advantages'oyer the one shown in Figs. 6 and 7 in that no attachment is placed on the armature ofrelay 504 in Figs. 8 and 9. Instead, the holding coil 503 is provided with an armature 802 and a restoring spring 803. A non-magnetic member 801 is pro vided and securely fastened to the armature 802 ofthe holding coil 503" so that, when the holding coil is energized, its armature 802 is attracted and the" armature or" relay 504 mechanically held in an operated condition while the winding thereof 15 deenerg1zed.'

504. With this mechanical arrangement in use in connection with the circuit of Fig. 5, a deenerg-ization' of the line relay as a result ofthe opening of the key on the associated line results in an opening of the .otherline and in an opening of the shunt around the holding coil associated with the other line. The outgoing line relay starts to deenergize and the holdin coil starts to ener ize at the v same time. By making the holding coil very.

quick to operate and very strong, the armature of; the holdin coil snaps uickl into,

its operated position and catches the armatureot' the outgoing line relay before it has hadtime to start to move.

Referring now particularly to Fig. 10, which shows a circuit similar to the one shown in Fig. 5, except that the holding coils ,in Fig. 10 are made into relays with spring combinations connected in parallel with the spring combinations of the respective asso: ciated line relays, no mechanical interconnec- 'tion is present between the several coils of Fig. 10. Assuming that such an arrangement as shown in F 1g. 10 .is w1red up and that the outgoing lines. are open, applying the bat-.

tery potential to the relays results in anenergization of both holding relays 1002 and 1003, each relay shortcircuiting the other at its inner contacts, the current limiting resistances 1005 and 1006 preventing a short circuitingof the current source. lnvariably, one of the holding relays falls back a little ahead of the a other and removes the short circuit fromthe winding of the other sothat the winding 01 the. other relay remains'operated. Assume that relay 1002 remains operated. In this case, line relay 1004 is connected to line east and the winding'ol relay 1003 is short circuit-U ed. If the line west be closed under this con Relay'1004 falls back and relay 1003 pulls up, short .circuiting thewinding of relay 1002 at its own contacts to prevent relay 1002 from becoming operated. The circuits remain'in this condition until line west is closed, whereupon relay 1001 operates and shunts the windings of relay1003 at its inner contacts, at the 1 same time connecting line east to relay 1004' at its lower contact. Belay 1004 now pulls up and the short circuited relay 1003 shortly falls back. 'Botliline relays are now operated and both holding relays are at normal.

Assume now that the operator online west sends. to line east.

each time itideenergizes' relay 1001 opens line east and removes the shunti rom around holding relay 1003. Relay 1003 operates and shunts the contacts of relay 1004, while relay Each break in line west results in a deenergizatmn of relay 1001 d I Li li 1004 responds to the impulses transmitted by relay 1001. Each time relay 1001 reoperates, the winding of relay 1003 is short circuited but the relay, being short circuited, is slow acting and with an ordinary adjustment does not fall back in the case of a succession of dots, but responds to a dash. In case a receiving operator opens his keyto interruptthe other operator, the sending line is not broken as long as the sending operator sends nothing longer than a dot, as relay 1003 is not short circuited (assuming the operator on line west to be sending) long enough to allow it to fall back and open the line west. lVhen line west becomes closed long enough for relay 1003 to fall back, however, the line west is opened and the operator thereon is notified of the break. In case it is desired that a receiving operator can break in in the middle of a train of dots and not have to wait for a dash to be transmitted, it is a very simple matter to increase the spring tension on relays 1002 and 1003 and to turn up the brass residual screws such as those shown in Figs. 6 to- 9 so that the armatures of the relays do not come close to the iron cores. When this is done relays 1002 and 1003 fall back on the transmission of each impulse, either dot or dash, and the receiving operator may break in at any time. It will be understood, of course, that a similar adjustment may be made in the case of Fig. 5 when used with the mechanical arrangement of Figs. 6 and 7 or with the me chanical arrangement of Figs. 8 and 9.

Referring now particularly to Fig. 11, this drawing shows a circuit having the same general aspects as the circuit of Fig. 10 but using a differential action to cause the release of the holding relays instead of a shunting action. It will be noted that the holding relays 1102 and 1103 are each provided with a Winding having a normally closed circuit through which current is normally flowin The other winding is differentially wound with respect to the first, so that in case a circuit is closed for the other winding of either relay the effect of the first winding is neutralized and the relay is thus deenergized. This arrangement has the advantage that no particular care need be exercised in securing a deenergization of the holding relay on the transmission of each impulse, as a differential relay has no noticeable tendency to be slow in releasing when current is passed through its second winding to deenergize it. It will be appreciated, 0t course, that the differential relays will not need to be entirely balanced, as any unbalance present may be tal en care of by increasing the spring tension slightly. It is perhaps preferable, in case of an unbalance in commercial windings, that the normally closed winding of the differential relay be made the weaker, thereby securing a very quick reversal of magnetism and a quick retraction of the armature when the circuit is closed through the slightly stronger winding. When the armature is thus retracted, it will not be reoperated due to the slight pull on account of the deenergizing winding being slightly stronger.

l/Vhat is claimed is:

1. In a telegraph system, two lines, a repeating device having two coils connected in' series with said lines, respectively, and arranged to be energized thereover, means responsive to a deenergization of either coil when the associated line is broken for breaking the other line, and additional means for energizing the coil of the other line in a local circuit while the other line is thus broken.

2. In a telegraph system, two lines, two coils connected in said lines, respectively, and arranged to be energized thereover, two relays arranged to be operated in. local circuits controlled by said line coils, respectively, and means responsive to a deenergization of either of said line coils when the associated line is broken for altering the local circuit of one of said relays, and contacts on said relays so that when the circuit of one of them is altered it opens the opposite line and connects the line coil of the opened line in a local holding circuit.

3. In a telegraph system, two lines, two single-coil line relays having their coils connected in said lines, respectively, two repeating relays controlled by said line relays, respectively, and contacts on each repeating relay for connecting the said line-relay coil of the opposite line either in series with the line or in a local circuit depending upon whether the repeating relay is energized or deenergized.

4. In a telegraph system, two lines, two line relays connected in series with said lines, repectively, two repeating relays associated with said line relays, respectively, contacts on each line relay closed when the relay is energized to close a local circuit for the,

associated repeating relay, contacts on each repeating relay closed when the repeating relay is energized to connect the opposite line relay in series with the line, and additional contacts on each repeating relay closed when the repeating relay is deenergized to connect the opposite line relay in a local holding circuit.

5. In a telegraph system wherein two lines are connected together through a two-way telegraph repeater including a single-coil line relay for each line, circuit connections in said telegraph repeater such that each linerelay coil may be disconnected from its asso ciated line responsive to the action of the other line relay, and circuit connections such that each line-relay coil is connected in a local holding circuit all the time that it is not connected to its associated line.

6. In a two-way telegraph repeater arranged to repeat impulses from either of two telegraph lines to the other, a line relay and a holding magnet for each line, each line relay having an armature free to move without interference from the associated holding magnet as long as the holdingmagnet is deenergized, each of said holding magnets having an armature and a restoring spring for maintaining the armature out of engagement with the armature of the associated line relay, and means responsive to a deenergization of either line relay when the associated line is broken for breaking the other line and for energizing the holding coil of the other line, the armatures of the holding coil and the associated line relay being so mounted relative to one another and so formed that the armature of the outgoing line relay is maintained operated mechanically by the armature of the associated holding relay.

7 A two-way telegraph repeater co1nprising two. line relays each having a contact actuating armature, two holding magnets associated with said line relays, respectively, and

veach having an armature separate from the armature of the associated line relay and also separately movable, the armature of each holding magnet being arranged to engage the armature of the associated line relay and hold it operated when the armature of the holding magnet operates, and circuit arrangements for automatically energizing the holding magnet associated with an outgoing relay when an incoming relay operates to break an outgoing line.

8. In a telegraph system wherein two telegraph lines are interconnected by a two-way telegraph repeater, said repeater comprising two line relays and two holding relays, contacts on each line relay for opening the opposite line and for energizing theopposite holding relay when the line relay falls back due to a break in the associated line,

and contacts on each holding relay for taking over the work of the associated outgoing relay.

9. In a telegraph system wherein two telegraph lines are interconnected by a two-way telegraph repeater, said repeater comprising two line relays and two holding relays, contacts on each line relay for opening the oposite line and for energizing the opposite olding relay when the line relay falls back due to a break in the associated line, and contacts on each holding relay connected in parallel. with the contacts of the associated line relay.

10. A two-way telegraph repeater comprising two line relays having contacts, two holding relays associated with the line relays, respectively, and contacts on each holding relay connected in multiple with the contacts of the associated line relay.

'In witness whereof, I hereunto subscribe my name this 28 day of November, A. D. 1928.

JOHN I. BELLAMY. 

